This invention relates to the molding of outer and inner soles onto shoe uppers, the outer sole consisting of an elastomer material and the inner sole consisting of a thermoplastic material, the inner and outer soles being joined together by a chemical bond between isocyanate contained in the thermoplastic material and reactive end group substances added to the elastomer. The apparatus has a vertically moveable upper cross block with a mold carrier mounted thereon for pivotal movement about a transverse axis, the mold carrier having a heatable first mold part at one end for the molding of outer soles in a molding position of the apparatus. A vertically moveable lower cross block has a mold plate in engagement with the first mold part in the molding position. The pivotable mold carrier together with lateral mold elements of the apparatus and a shoe last-mounted shoe upper cooperate together to define a cavity for the molding of the inner sole.
The molding apparatus may be located at each of a plurality of molding stations on a circular turntable for carrying out the molding operation.
German patent No. 22 41 493 discloses shoes with an inner sole of polyurethane and an outer sole also of polyurethane.
Circular turntable installations providing a plurality of molding stations are generally disclosed in Publication No. DESMA 521S-526S, Klockner-Ferromatik Desma GmbH, and entitled "Injection Molding Machine For Direct Attachment Of Soles." The circular turntable installations have two devices for the mixing of isocyanate and a polyol into a mixture reacting into polyurethane which, depending on the mixing ratio and the additives, reacts into a wear-resistant outer sole or a flexible inner sole.
The circular turntable is rotated incrementally for molding the outer soles and the inner soles. The molding stations are stopped during incremental movement and interlocked when stopped relative to the two mixing and injection devices.
These devices are located along the periphery of the turntable and are movable in a radial direction toward the turntable. The molding apparatus at each station has two lateral molding elements which, in a mold closed position, define an opening and two sprue channels.
A vertically moveable last turning body is mounted on the apparatus above the lateral mold elements, the body having a counterstamp and a shoe last for supporting the shoe uppers.
A vertically adjustable bottom stamp is located below the lateral mold elements. The bottom stamp, lateral mold elements in their mold closing position and the counterstamp together define a mold cavity into which the mixture reacting into the outer sole is introduced.
The bottom stamp which contains the molded outer sole, the lateral mold elements in a mold closed position, and the shoe last which supports the shoe upper together define a mold cavity for molding the inner sole as the mixture reacting into the inner sole is introduced into the mold cavity which, in the course of the reaction, bonds to the outer sole and to the shoe upper.
U.S. Ser. No. 942,832, among the aforementioned related applications, discloses molding stations on a circular turntable for the molding of shoe soles with an outer sole of elastomer and an inner sole of polyurethane.
For the molding of the outer sole of elastomer, there is provided, in lieu of a previously employed device for mixing the mixture reacting into polyurethane, a plastification and injection aggregate device for plastification of the elastomer, as employed in injection molding machines for the processing of thermoplastic synthetic materials, and for injection of the elastomer into the outer sole mold cavity. Since high pressures occur during the injection of the plastified elastomer, the molding apparatus at each station is provided with an upper, vertically adjustable cross block supporting a pivotably mounted mold carrier with pairs of opposing heatable mold parts lying parallel to the pivot axis, each mold part defining a mold cavity for the outer sole and including cooling channels.
A lower, vertically adjustable cross block below the first cross block has a heatable plate facing the mold carrier and cooperates with the heatable mold parts thereof for the production of outer soles. Above the upper vertically moveable cross block is a fixed cross block having an opening into which a heatable mold part with a molded outer sole in its mold cavity projects and combines together with laterally movable mold elements, located above the fixed cross block, for the molding of an inner sole of polyurethane.
The mixtures which react into polyurethane for the outer sole and/or for the inner sole essentially consist of a polyol and isocyanate, as well as chain extenders and catalysts, which are adjusted by the respective additives for the desired material properties of the outer soles and/or inner soles, whereby the outer sole is rendered wear resistant and the inner sole flexible having a porous structure.
The chemical reaction starts with the mixing of the components. In the mold, the mixtures react into outer soles or inner soles. During the reaction into the inner sole, the molding of the sole takes place simultaneously with the bonding to the shoe upper and to the outer sole.
The outer sole of elastomer and the inner sole of polyurethane are bonded in the area of their contacting surfaces by chemical bonds between isocyanate and reactive end groups of the substances added to the elastomer.
As likewise employed for the present invention, the mixtures reacting into polyurethane are mixtures on the basis of ether or esterpolyols, containing on the basis of 100 parts by weight:
30-100 parts by weight isocyanate; PA1 0.1-10 parts by weight catalyst; PA1 the remainder chain expanders; and PA1 other usual additives. PA1 Vulkadur A (Bayer AG) PA1 Coretack (BASF) PA1 SP 1045 (Krahn) PA1 Korever (BASF) PA1 Cohedur A (Bayer AG) PA1 Cohedur RS (Bayer AG) PA1 Cohedur RK (Bayer AG) PA1 Vulkasil S (Bayer AG PA1 Ultrasil (Degussa) PA1 3-amino-propanol PA1 Stearylamine PA1 Mowiwol (Hoechst) PA1 VSH 72 (AIR PRODUCTS) PA1 VSH 73 (AIR PRODUCTS) PA1 Formrez (Witco) PA1 Hydrin (Polysar) PA1 Hercolor (Hercules) PA1 or a combination of the above substances.
The catalyst which may be used is DABCO-SB produced by Airproducts Company.
The outer soles are made from elastomers which can be mixed with the following chemical compounds or chemical substances in quantitative shares of 0-20 phr, relative to the rubber amount: e.g., acryl-nitryl-rubber, styrol-butadiene-rubber, natural rubber, chloroprene-rubber.
The outer soles can generally be produced from any known rubber quantities if, for example, the following substances are mixed in quantities of 0-20 phr (quantity relative to the amount of rubber used):
phenolformaldehyde resins, e.g. PA0 methylolized phenolformaledhyde resins, e.g.: PA0 resorcin in connection with a formaldehyde dispenser, e.g.: PA0 silicic acid fillers, e.g.: PA0 aminoalcohol, e.g.: PA0 primary or secondary amine, e.g.: PA0 polyvinylalcohol, e.g.: PA0 high hydroxylgroup containing polyol, e.g.: PA0 Acrylate rubber (ACM) e.g.:
The formation of the outer sole of the elastomer is carried out in such a manner that the elastomers plastify at the usual processing temperatures and are injected into the mold cavities according to the usual technology and corresponding high pressures of injection molding machines.
The control of the temperature of the elastomers is carried out such that the temperature of the injected outer soles is cooled to just below the decomposition temperature of the polyurethane for the inner sole to be produced and then the mixture reacting into the polyurethane is brought into contact with the outer sole, whereby in the contacting surfaces between the elastomer and the reacting polyurethane isocyanate reacts with the reactive end groups.
Taken into account in the control of the temperature of the elastomer is that a temperature increase or a temperature reduction of 10.degree. C. leads to a shortening or lengthening of the vulcanization time, i.e., the time needed for the elastomer to complete its reaction, by 50%.
One of the problems encountered with the molding apparatus of the aforementioned published application is that the cooling rate of the molded outer sole of elastomer to the temperature at which the mixture reacting at the polyurethane for the inner sole is introduced into the mold cavity for the inner sole is essentially determined by the high heat capacity of the mold parts located on the pivotable mold carrier. This cooling rate has the effect that the time required for the molding and cooling of an outer sole is considerably longer than the time required for molding the inner sole.